The Smithsonian Institute has released a fascinating video that captures X-Ray footage of a bat in mid-flight.

Bats are the only mammals capable of sustained flight. That’s pretty amazing, but also raises quite a few questions, which is why researchers at Brown University aim to find out exactly how the mechanics of their flight-ability work. They have been filming fruit bats take off into the air using an X-Ray camera and integrating the data with 3D-models of the bat’s skeleton.

The integration of 3D models and video used in the research is known as X-ray Reconstruction of Moving Morphology (XROMM), and has led to some interesting findings for the team, led by Nicolai Konow: Conventionally, tendons in mammals are thought to be stiff, thick, and unstretchable, but the fruit bat proves this theory wrong. The bat is capable of stretching the tendons connecting their biceps and triceps to their skeletons, and then compress them to release energy to help them fly.

The finding was confirmed by flouromicrometry, a technique in which chemical markers are injected into the bat’s muscles that allow the researchers to measure the changes in muscle length during extension and compression. Check out the video at the Smithson Institute!